crypto: arm/blake2s - fix for big endian

The new ARM BLAKE2s code doesn't work correctly (fails the self-tests)
in big endian kernel builds because it doesn't swap the endianness of
the message words when loading them.  Fix this.

Fixes: 5172d322 ("crypto: arm/blake2s - add ARM scalar optimized BLAKE2s")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>